Conventionally, a connector includes a contact group, and an insulator which holds the contact group. Each of contacts constituting the contact group has a terminal portion which is to be connected to a connection object, and a contact portion which is to be connected to a counter contact. In the range extending from the terminal portion to the contact portion, the contacts are in parallel in the fitting/unfitting direction of the connector and the counter connector. The contacts are arranged at equal pitch in the pitch direction which is perpendicular to the fitting/unfitting direction so that the distances between adjacent contacts are equal to one another. The arrangement of the contacts at equal pitch supports the cost reduction, improvement of the productivity, miniaturization, and pitch reduction of the connector.
In the differential transmission, when the distance between paired (differential pair) adjacent signal contacts is equal to that between a non-paired contact (i.e., a contact except contacts constituting a contact pair) which is placed on both adjacent sides or one adjacent side of the paired signal contacts, and one of the signal contacts, however, the differential coupling force between the paired signal contacts is weakened by crosstalk from the signal contact to the non-paired contact, and disadvantages such as signal reflection and noise radiation are caused by impedance mismatching due to the connector, thereby producing a problem in that transmission cannot be efficiently conducted.
On the other hand, Patent Literature 1 discloses a configuration where terminal portions are arranged at equal pitch, and contact portions are placed so that the distance between contact portions of paired signal contacts is shorter than that between contact portions of external and signal contacts, thereby suppressing crosstalk to enhance the differential coupling force.